Though the programmed cell death of the tapetum is one of the most critical and sensitive steps for fertility and is affected by various environmental stresses,its regulatory mechanisms remain mostly unknown.Tapetal death is essential for the provision of many molecules required for pollen development.Tapetal breakdown resembles apoptotic programmed cell death(PCD),being relatively rapid and involving cell shrinkage,DNA fragmentation and mitochondrial and cytoskeletal disintegration.TDR(Tapetum Degeneration Retardation)is a basic helix-loop-helix(bHLH)domain transcriptional regulator that promotes tapetal cell development and post-meiotic microspore formation by binding DNA and regulating gene expression.TDR and its Arabidopsis ortholog AMS(Aborted Microspores)play important roles in anther development in rice and Arabidopsis,respectively.By in-depth analyzing the transcriptomic data of mutants of TDR and AMS,and combining with gene microarray analysis and tobacco-yeast transformation,the putative executor of anther tapetum PCD,cysteine proteases,will be screened and identified from downstream targeted genes of TDR/AMS.To explore the genetic and biochemical functions of the key cysteine proteases in anther development and tapetum PCD,further genetic analysis on relevant mutants and caspase-like activity analysis will be performed.On one hand,the present project hope to provide a theoretical basis for exploring the mechanism of pollen fertility modulation and its application to practical breeding by uncovering the functions of cysteine proteases/genes in anther development and tapetum PCD in plant.On the other hand,this project hope to explore the regulatory differences between animal PCD and plant PCD from a biochemical and molecular evolutionary respective by both in vivo and in vitro biochemical characterizing the caspase-like activities of these cysteine proteases.